The goal of this project is to obtain information about the physiological properties and anatomical interrelationships of neurons in the mammalian retina. The aspects of retinal physiology and anatomy with which we have dealt in the past annum are: the spectral classes of photoreceptors in cats and rabbits and the chromatic interactions among the cones; the morphological basis of the ON center and OFF center pathways of the cat retina, and a comparison of the response properties of single units in the parallel rod and cone pathways of both cats and rabbits; and finally, the pharmacological role of the cyclic nucleotides in the responses of mammalian rods. At the single unit level, electrophysiological recordings have been made, both intracellularly and extracellularly, and single units have been intracellularly injected with a variety of stains. Anatomically the synaptic interrelationships of single units have been studied electromicroscopically in serial ultrathin sections, and in the light microscope such single unit reconstructions have been compared to similar units stained with the Golgi technique, or to units electrophysiologically studied and stained. At the multi-unit level the massed responses of retinal neurons as reflected in the electroretinogram have been studied. BIBLIOGRAPHIC REFERENCES: Nelson, R., Kolb, H., Famiglietti, E.V., and Gouras, P.: Neural responses in the rod and cone systems of the cat retina: Intracellular records and Procion stains. Invest. Ophthalmol. 15: 946-153, 1976. Nelson, R.: Cat cones have rod input: A comparison of the response properties of cones and horizontal cell bodies in the retina of the cat. J. Comp. Neurol. 172: 109-136, 1977.